CAPE
CANAVERAL, Fla. -- The weather forecast for Friday?s evening liftoff of the
shuttle Atlantis has improved and NASA officials are optimistic launch will
take place as planned.

?After many
months of hard work, Atlantis is nearly ready to fly,? said NASA test director
Steve Payne Thursday in a mission briefing here at the Kennedy Space Center
(KSC) spaceport. ?We are currently tracking no significant issues on the
vehicle.?

Dark, heavy
clouds poured rain and spouted lightning around KSC Wednesday evening, but the
shuttle launch facility was spared the brunt of the storm?s fury.

Instead,
most of the rain and even three-quarters inch hail fell some 50 miles (80
kilometers) south of KSC.

?We did
have some significant weather in the area last night, but luckily, most of it came
together in Melbourne, as opposed to up here over the launch pad,? said NASA
shuttle weather officer Kathy Winters.

Forecasters
predict favorable weather conditions for Friday evening, when Atlantis is
slated to loft into space at 7:38 pm EDT (2338 GMT) with the seven STS-117
astronauts. Atlantis' astronaut crew, commanded by veteran
spaceflyer Rick Sturckow, is tasked with delivering and installing two new
truss segments and a pair of starboard
solar arrays at the International Space Station (ISS).

The current
forecast gives an 80 percent chance that Atlantis will launch on time?up from
70 percent yesterday. Favorable weather is also predicted for NASA?s
contingency landing sites in the U.S. and Europe, Winters said.

In case of
a delay, the weather forecast for Saturday and Sunday drop to 70 and 60
percent chance ?Go,? respectively.

?Overall,
the first day is the best day for the overseas site and the U.S. site and also
Kennedy Space Center,? Winters said.

Atlantis
has an open launch window from June 8 to 12, after which it will have to stand
down for four days to make room for a planned rocket launch on June 14. The
window reopens on June 17 and runs through mid-July.

The shuttle
was originally slated to fly on March 15, but was delayed when a freak
thunderstorm peppered the Atlantis' foam-covered external tank with hail, leaving
thousands of defects that had to be repaired.

?We have
complete confidence in our repair technique, and we expect it to perform, as
did STS-96? when Atlantis had to be similarly repaired, said Rob Worthy, NASA
vehicle manager for Atlantis' fuel tank and solid rocket boosters. ?We feel
that we are safe and ready to fly.?

Today, the
STS-117 astronauts are scheduled to accompany their friends and family on
special guest tours of KSC, as well as sit on a series of briefings related to
launch and practice shuttle landing in a modified Shuttle Training Aircraft
(STA).

The first
of four scheduled holds in the launch countdown will commence at 1:00 p.m. EDT (1700
GMT) today, and will last for four hours. The rotating service structure that
protects the shuttle is expected to be retracted later tonight, and fueling for
launch is scheduled for tomorrow morning.